PURPOSE: To make it possible to obtain a stable slide between a ball and a ball seat in a compressor for a refrigerator or the like, by forming an annular groove into which a bevel shape press-fit spring is engaged, in the inner wall of a ball joint type piston, adjacent to a step in an inclined part.
CONSTITUTION: The bore diameter D of a cavity 14' in a piston 14 is made to be larger than the diameter of skirt part 18' of a bevel shape compression spring 18, and an inclined part step 21 which is so inclined that the cavity is narrower and narrower inward is formed in the inner wall surface of the piston 14. Further, an annular groove 19 is formed adjacent to the step 21. When the bevel shape compression spring 18 is pushed into the cavity 14' in such a condition that the ball member 17 on a connecting rod 16 is made into contact with a ball seat 15 in the piston 14, the inclined part step 21 pushes the skirt part 18' which is therefore fitted into the annular groove 19 without the inner surface of the piston being scratched. Thus, the skirt part of the compression spring may be fitted into the piston groove always in the horizontal direction, thereby it is possible to stably obtain a slide between the ball on the connecting rod and the piston ball seat.
SASANO HIROSHI
OOTA TOSHIHIKO
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